Photoluminescence properties of far-red emitting Lu2CaAl4GeO12:Cr3+ garnet phosphor

The Cr3+-doped garnet structural phosphors were widely investigated for phosphor-converted light-emitting diode. Here Cr3+ activated Lu2CaAl4GeO12 phosphor with far-red emitting was prepared using the solid-state reaction method. The crystal structure was analyzed employing X-ray diffraction technique. A broad excitation band in the 400–500 nm region was found in the excitation spectrum, which matches well with the chip that emits blue light. The sample exhibits sharp line (2E → 4A2) and broad emission band (4T2 → 4A2) of Cr3+ ions under the 428 nm light excitation. The concentration quenching is mainly caused by the energy transfer between the nearest Cr3+ ions in the host. The thermally stable luminescence was observed by measuring the emission spectra in the temperature range from 300 K to 620 K. The overall emission intensity reaches about 109% at 420 K and maintain 81.4% at 620 K compared to the value at 300 K. This work facilitates the study of Cr3+-doped garnet phosphor with thermally stable far-red emitting.